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WATCH: Shi'ite groups in Pakistan added their voices to protests around the world against Saudi Arabia's execution of prominent Shi'ite cleric, Sheikh Nimr al-Nimr. Hundreds of protesters gathered in Karachi and chanted death to the Saudi royal family. (RFE/RL's Radio Mashaal)

Saudi Arabia has dismissed concerns that its severance of ties with Iran will harm efforts to negotiate peace in Syria even as its actions have opened up a new sectarian rift among opposing sides in the war.

A top Syrian opposition group urged all Arab countries on January 4 to follow the Saudi example and end diplomatic ties with Iran, while four Saudi allies -- Bahrain, the United Arab Emirates, Kuwait, and Sudan -- all moved to cut off or downgrade their ties with Tehran.

Kuwait said on January 5 that it had recalled its ambassador to Iran while Sudan's state media reported Khartoum has given Iranian diplomats two weeks to leave the country.

UN Secretary-General Ban Ki-Moon, the United States, and Britain all voiced concern on January 4 that the Saudi-Iran split has laid bare and could worsen a sectarian divide that has simmered beneath the Syrian conflict and the broader Middle East for decades -- setting back efforts at peace.

Iran's regime, led by Shi'ite Islamic clerics, backs the government of Syrian President Bashar al-Assad, while the Sunni monarchs who hold power in Saudi Arabia and other Persian Gulf states back many of the rebel groups fighting the government.

Together, the two regional powers and their allies, along with the United States, Russia, and other world powers, have been seeking to arrange a peace process for Syria that has foundered in the past because of such stark differences.

"From our side, it should have no effect because we will continue to work very hard to support the peace efforts in Syria and Yemen," Saudi Ambassador to the United Nations Abdallah al-Mouallimi said on January 4.

Saudi Arabia "will attend the next Syria talks and we are not going to boycott them because of Iran," he said, even as he took a swipe at Iran's role in the peace negotiations.

"The Iranians even before the break of diplomatic relations have not been very supportive, not very positive in these peace efforts," Mouallimi said.

"They have been taking provocative and negative positions...and I don't think the break in relations is going to dissuade them from such behavior."

He spoke as the UN dispatched Syrian envoy Staffan de Mistura to Tehran and Riyadh to try to ensure the conflict does not derail negotiations scheduled for January 25, while the UN Security Council debated a statement addressing the Saudi-Iranian tensions.

UN Secretary-General Ban spoke by phone with the Saudi and Iranian foreign ministers to urge them to "avoid any actions that could further exacerbate the situation," Ban's spokesman Stephane Dujarric said.

"A breakdown of relations between Riyadh and Tehran could have very serious consequences for the region," Dujarric said.

The UN Security Council late on January 4 issued a statement urging the two sides to "maintain dialogue and take steps to reduce tensions" while condemning the sacking and burning of Saudi Arabia's embassy in Tehran by demonstrators on January 2.

But Ban took Iran's side on the kingdom's execution of 47 men over the weekend, including a prominent Shi'ite cleric, which prompted an outpouring of rage among Shi'a throughout the Muslim world.

Ban said he was "deeply dismayed" by the executions, prompting a curt response from the Saudi's UN mission, which insisted that those executed had been "criminals" who had "fair and just trials without any consideration to their intellectual, racial, or sectarian affiliation."

Shi'ite Sheikh Nimr al-Nimr, a fiery critic of the Saudi authorities, was sentenced to death in 2014 on charges of causing sectarian strife and disobeying the ruler. His trial was condemned as unfair by human rights groups and his supporters say he had only called for peaceful protests.

Like Saudi Arabia, Bahrain and the Gulf Emirates are dealing with restive Shi'ite minorities, and both accused Iran of interfering with their internal affairs as the reason for curbing diplomatic relations on January 4. Sudan said it was acting in "solidarity" with Riyadh.

The Turkey-based Syrian National Coalition, a top Syrian opposition group, also declared its support for Riyadh and criticized what it said was Iran's support for militias in Syria and Iraq.

Also rallying behind Riyadh was the Arab League, which has scheduled talks on January 10 on the split with Tehran.

White House spokesman Josh Earnest urged the two sides to calm down and said the United States had raised concerns with Riyadh about executing the Shi'ite cleric for fear it would provoke a backlash in the Shi'ite world like the one that came to pass.

Now, the United States is concerned that the flare-up between Iran and Saudi Arabia will derail the Syrian peace effort spearheaded by U.S. Secretary of State John Kerry, he said.

"It was very difficult to get everybody around the table. It certainly is going to be even more difficult to get everybody back around the table if you have the Saudis and the Iranians trading public barbs and public expressions of antagonism," Earnest said.